This application claims priority of prior foreign applications 1997 2940/97 and 1998/1065/98, filed on Dec. 22, 1997 and May 13, 1998, respectively, the disclosure of which is expressly incorporated by reference here.
The present invention relates to a vacuum treatment system having a vacuum chamber, and at least one rotatably driven part lo within that chamber, which rotatably driven part is connected by way of a transmission comprising at least two mutually rolling-off rotational transmission bodies with a motor-type drive unit.
The present invention is addressed to problems which occur during vacuum coating, particularly of optical disks, particularly of rewrite disks. However, the findings made here can also easily be applied to other vacuum treatments; in principle, wherever a part must be rotatably driven in a vacuum treatment chamber of a system.
It is known to provide substrate carriers on planet wheels of a planetary transmission, for example, for sputtering systems, in order to implement, by way of a sputtering source, while utilizing maximal fractions of sputtered-off material on the substrates, a distribution of the applied layer thickness which is as homogeneous as possible. For the rotary drive, normally gear-type transmissions are used in the vacuum atmosphere.
It is disadvantageous to use such transmissions in the treatment vacuum of the system, particularly because of occurring abrasion and the resulting contamination risk to the built-up layers, but also with respect to the development of noise, friction-caused lossesxe2x80x94because lubricants suitable for a vacuum have relatively poor lubricating propertiesxe2x80x94and, as a result, because of the short service life after which rotational transmission bodies having gears have to be replaced.
A system having a planetary transmission is described in DE 196 49 412. In that system, the addressed problems are solved in that the sun and planet system is constructed twice, specifically without gears on the interior side of the vacuum chamber and geared on the exterior side of the vacuum chamber. The sun system on the interior side of the vacuum chamber is driven by a shaft extending through the vacuum chamber wall, while the planets on the interior side of the vacuum chamber which have the substrate carriers are driven by magnetic couplings which are established through chamber wall sections with planets on the outside of the chamber.
This approach using magnetic couplings requires extremely high expenditures. Concerning magnetic rotation transmission devices on pumps, reference is made to U.S. Pat. No. 4,850,821 or 5,449,276.
An object of the present invention is to provide a vacuum treatment system which, although a transmission is provided in the vacuum, which in DE 196 49 412 is displaced to the outside, is capable of eliminating the above-indicated disadvantages. For this purpose, the system according to the invention is characterized by the at least two rotational transmission bodies being operatively coupled magnetically.
In the present case, a roll-off movement is a movement during which the above-mentioned rotational bodies can move as if they rolled off on one another, but for this purpose, because of the magnetic coupling, do not necessarily have to be in contact with one another.
In a first currently preferred embodiment, the motor-type drive for the above-mentioned transmission is arranged outside the vacuum chamber, and the driving of the transmission takes place by way of a shaft extending in a vacuum-tight manner through the vacuum chamber wall or by way of a magnetic coupling which acts through the wall of the vacuum chamber from the drive upon the transmission. In another currently preferred embodiment, while the drive is situated on the outside, the magnetic drive coupling of the mutually rolling-off rotational bodies takes place by way of the chamber wall. As a result, the drive coupling and the transmission through the chamber wall are implemented simultaneously.
On their periphery, the rotational transmission bodiesxe2x80x94analogous to the gearing of such rotational bodies on geared transmissionsxe2x80x94have permanent-magnet segments which, as a result of a mutual attraction or repulsion, in this case, preferably by mutual attraction, ensure the magnetic drive transmission.
In still another currently preferred embodiment, the transmission is constructed as a planetary transmission in which the sun wheel is operatively connected with the motor-type drive unit, and the planet wheels are magnetically coupled with respect to the drive.
By replacing the gears on geared transmissions by xe2x80x9cmagnet gearsxe2x80x9d which are arranged at uniform distances from one another on the participating rotational bodies and xe2x80x9cengage in one anotherxe2x80x9d preferably by mutual attraction, or by repulsion, depending on the usage, the transmission types can be implemented which are known from geared transmissions; for example, by providing xe2x80x9cmagnetically gearedxe2x80x9d spur gears, wheels with internal gears, bevel gears, worm gears, crown gears, etc. In principle, it is achieved according to the invention that the drive-transmitting rotational bodies of the transmission no longer result in abrasion, the resulting transmission has a much lower friction than analogous mechanical, geared transmissions, and thus require a significantly reduced driving power, in that lubrication problems and therefore also problems concerning a reduced service life are significantly reduced.
Using the principle according to the invention, it is also possible to suggest a sputtering process according to the invention which exhibit s a hardly surpassable process homogeneity on the workpieces.